The present invention relates generally to flow control valves and more particularly to a flow control valve which regulates coolant flow to a heater core.
Heater cores such as those used in automotive vehicles receive hot coolant from the engine. The rate of coolant flow is proportional to engine speed (rpm). It is known that over the life of a vehicle the coolant may be contaminated with particles of grit, rust, etc. which also flow through the core. In order to increase the useful life of the heater core and protect it, it is necessary to limit the flow rate of the coolant through the heater core to reduce erosion due to the impact of the particles with portions of the core. Further, during the useful life of the heater core sediment within the coolant may accumulate on the various internal passages of the heater core which tends to restrict the flow of coolant therethrough. Consequently, as the heater core ages the pressure drop across the core increases. It is also useful to limit the maximum flow rate of coolant through the heater core to maintain the pressure within the core at reasonable levels otherwise the core may flex, leak or fatigue prematurely. It has been found that if the flow rate of coolant is restricted to approximately 5-6 gallons/minute ( 19-23 liters per minute) heater core useful life can be increased. The above relationship has been appreciated for some time. Current heating systems utilize a rubber orifice flow control washer. This device provides a restriction at all flow rates. As the flow pressure increases the rubber compresses causing the flow area (orifice diameter) to decrease thus limiting the flow to the required amount. While the rubber orifice functions to limit the maximum flow rate of coolant, it also provides a significant restriction to the flow of coolant at lower engine rpm thus restricting the amount of coolant communicated to the heater and reducing its performance.
It is an object of the present invention to provide a flow control valve for a heater core which maximizes flow at low engine rpm and which limits coolant flow to approximately 6 gallons per minute at high engine rpm. Another object of the present invention is to controllably terminate coolant flow to the heater core under certain conditions such as when maximum air conditioning performance is required.
Accordingly, the invention comprises: a heater control valve comprising: a valve body defining a chamber and a bypass passage extending therefrom, first conduit means in fluid communication with the bypass passage for defining a first inlet port adapted to receive coolant and a first exit port adapted to communicate coolant to an external device such as a heater core, including flow diverter means to urge coolant to flow into the diverter passage. The control valve further comprising second conduit means, in communication with the chamber for defining a second inlet adapted to receive flow from the external device and a second outlet. The valve body further including a first seating surface disposed about an upstream end of the bypass passage and a second seating surface disposed about the second inlet. A bypass valve, is located in the valve body, rotatable from a first position in sealing engagement with the first seating surface to a second position in sealing engagement with the second seating surface and, includes a hinge pin extending from the valve body; and actuator means for rotating the hinge pin and bypass valve from the first position to the second position in response to control signals and for generating a bias force upon the bypass valve to maintain same in sealing engagement with the first seating surface below coolant flow rates less than a predetermined level wherein the bypass valve is permitted to rotate against the bias force, under the action of the fluid force generated by the diverted coolant to regulate coolant flow at the first outlet at the predetermined level.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.